Reduce to lowest terms: $- \dfrac{3}{8} \div \dfrac{7}{2} = {?}$
Explanation: Dividing by a fraction is the same as multiplying by the reciprocal of the fraction. The reciprocal of $ \dfrac{7}{2}$ is $ \dfrac{2}{7}$ Therefore: $ - \dfrac{3}{8} \div \dfrac{7}{2} = - \dfrac{3}{8} \times \dfrac{2}{7} $ $ \phantom{- \dfrac{3}{8} \times \dfrac{2}{7}} = \dfrac{-3 \times 2}{8 \times 7} $ $ \phantom{- \dfrac{3}{8} \times \dfrac{2}{7}} = \dfrac{-6}{56} $ The numerator and denominator have a common divisor of $2$, so we can simplify: $ \dfrac{-6}{56} = \dfrac{-6 \div 2}{56 \div 2} = -\dfrac{3}{28} $